The art of rolling bales of fodder, such as hay or straw, by rolling up a swath or windrow on the ground like a carpet has only been known since 1963, when U.S. Pat. No. 3,110,145 issued to Philip John Avery, who had obtained related patents on the subject in Australia and the United Kingdom in the same year. Commercial interest in such balers in the United States dates only from about 1970. Since that time there have been a number of machines developed for rolling a swath of fodder into a bale on the ground, some of which have been improvements upon the original Avery concept, while others have employed mechanically distinct approaches. There has been a trend toward making extremely large bales which may be six feet in diameter and contain a ton or more of hay; and such mammoth bales have been made either by ground engaging balers or by chamber type balers.
Various workers in the agricultural equipment industry have sought to improve upon the quality of the bale produced by a rotary baler, and in particular a rotary baler of the type which rolls the bale on the ground. One of the most complex problems has been that of achieving the most complete possible pickup of fodder in the swath for incorporation into the bale; and another difficult problem has been that of achieving a desired bale density. Prior art patents which are particularly directed toward solving these problems are Beebout U.S. Pat. Nos. 3,680,296, issued Aug. 1, 1972; Kopaska 3,797,215, issued March 19, 1974; and Lundell 4,019,309, issued Apr. 26, 1977.
In addition, the related co-pending application of Kampman, Ulrich and Hodgson, Ser. No. 719,064 filed Aug. 30, 1976 which is now U.S. Pat. No. 4,103,475 is directed primarily to the problem of producing a bale which is somewhat loose in the middle and has a small amount of a relatively high density material around the outside.